How to add external training in chatterbot?
I'm not sure if this is the right one, but according to the documentation you need to create a trainer for it:

from chatterbot.trainers import ChatterBotCorpusTrainer

# Create a new trainer for the chatbot
trainer = ChatterBotCorpusTrainer(chatbot)

# Train based on the english corpus
trainer.train("chatterbot.corpus.english")


Instead of "chatterbot.corpus.english" you obviously choose your own training data.